Silencer



July 18, 1939. H. MARTIN 2,166,670

SILENCER Filed Sept. 13, 1938 WM 77% m Afarzuzy Patented July 18, 1939 UNITED STATES PATENT OFFICE SILEN CER.

Herbert Martin, Esslingen-on-the-Neckar, Germany, assignor to J. Eberspacher, Esslingen-zonthe-Neckar, Germany 1 Claim. (Cl. ISL-56) This invention relates to silencers, especially for internal combustion engines.

Silencers have beenv proposed in which several chambers are arranged in series and are con- 5 nected with each other by a single pipe. These silencers have only a limited silencing effect because the resonance of each single connecting-pipe is excited by the whole sound energy and is transmitted to the following chamber at the orifice of the pipe, 1. e. only in one single place. Consequently the excitement in this chamber takes place in one single plane only. Owing to this, the sound energy is not uniformly distributed over the chamber, which is unfavorable for. the silencing effect.

Furthermore silencers have been proposed in which the several chambers are connected with one another by a plurality of pipes having the same diameter and length, the orifices of the pipes lying in one and the same plane.

In this type of silencers the resonance and the excitement, in the chambers also take place in one plane only whereby the sound energy is again distributed in an irregular manner.

Finally another type of silencers has been constructed in which the-single chambers are connected with one another by several pipes of different length and diameter. Consequently these connecting pipes have different acoustic conductive valuesji. e. the sound energy transmission of the connecting pipes is of different intensity.

With this construction that part of the sounds energy which is transmitted by the connecting pipe having the greatest acoustic conductive value is decisive of the transmission into the next chamber of the sound, that is to say this fraction of sound is accentuated to a considerable extent and superposes itself upon the other fractions of energy in the other connecting pipes.

The present invention relates to silencers in which several chambers arearranged in series which are two and two connected by several pipes having different lengths and cross-sections. The invention now consists in making the ratio of the free cross-section to the length equal for all the connecting pipes, and in locating the inlet and outlet openings of the connecting pipes in different planes perpendicular to the direction of the sound transmission.

An embodimentof my invention is illustrated in the annexed drawing of which Fig. 1 is a longitudinal cross-section, and

Fig. 2 is a cross-section along the line II of Fig. 1.

The sound current arriving through the tube a enters the chamber b and is transmitted through the pipes c, d, and 6 into the chamber 1. The chambers b and ,f are separated from each other by the partition g. Any number of further chambers may join the chamber communicating with one another inthe same manner as the chambers b and f. The current is withdrawn from the last 10 chamber through the tube h.

The pipes c, d, and e have always the same ratio of cross-section to length, i. e. each of them has the same acoustic conductive value. Consequently the sound current flows through these pipes 15 always with the same intensity. Correspondingly the excitement and the'transmission at the orifices of the pipes c, d, and e takes place always with the same intensity, and therefore a uniform distribution of the energy takes place in the chambers, whereby an effective silencing is attained.

As all the pipes have the same acoustic conductive value, the same fundamental frequence results in cooperation with the chambers so that the sound transmission into each of the following chambers takes place in a uniform manner.

Moreover the inlet and the outlet openings of. the connecting pipes c, d, and e are not located in one and the same plane, but the sound energy is withdrawn and transmitted at different places. Consequently the excitement by the sound current when leaving the connecting pipes c, d, and e takes place in such a manner that the single sound planes extend drawn asunder in spaced condition. Therefore also by this arrangement the silencing effect is increased, the sound energy in the adjacent chamber being quite uniformly distributed by the equal sound current coming from each of the outlets of the pipes c, d, and e.

I claim:

A silencer, especially for internal combustion engines, comprising several vessels arranged in series, a plurality of pipes connecting at any time two successive vessels with one another, the 45 pipes having different lengths and cross-sections, the ratio of the. free cross-sectional area to the length being the same for all the pipes, and the inlet and outlet openings of the connecting pipes being located in different planes perpendicular to the direction of the sound transmission.

' HERBERT MARTIN. 

